Actuators for pressure loaded valves

ABSTRACT

Hydromechanical control devices for valves which are normally held in the closed position against applied fluid pressure are disclosed. The control devices include a differential area piston mechanically linked to the valve and acted upon by fluid furnished from an accumulator system. The force resulting from the application of system pressure to the small area end of the piston counterbalances the normal applied pressure thereby holding the valve closed and valve opening is achieved by placing the large area end of the piston in communication with the accumulator system.

United States Patent 1 1 3,601,357

121 Inventor Edouard Legille 6 References c1160 5 Luxemmurg Grand Bud! UNITED STATES PATENTS 1 192 635 9/1916 Hod kinson 251/58 x I] pp No. 850,914 g [22] Filed A 18 1,512,804 10/1924 Roucka 91/47 x ug. 1969 [45] P 2,848,873 8/1958 Levetus ct al 91/5 X meme! ml 3 155 365 11/1964 Hartung @1611 251/25 [73] Asmgm @352 Eubmmm's P 3:375,658 4/1968 Slover 91/5 x Luxeml ,Luxembourg 3,467,129 9/1969 Gratzmuller 251/25 X [32] Priority Aug. 19, 1968 Primary Examiner-Arnold Rosenthal [33] Luxembourg Attorney- F ishman and Van Kirk 1 1 56,736

ABSTRACT: Hydromechanical control devices for valves which are normally held in the closed position against applied 54] ACTUATORS FOR PRESSURE LOADED VALVES fluid pressure are disclosed. The control devices include a differennal area piston mechanically linked to the valve and v 2 Claims, 2 Drawing Figs.

acted upon by flu1d furnished from an accumulator system. [52] US. Cl, 251/25, The force resulting from the application of ystem pressure to 25 /58, 91147 the small area end of the piston counterbalances the normal [51] Int. Cl F16k 31/163 applied ressure thereby holding the valve closed and valve [50] Field of Search 251/25, 26, opening is achieved by placing the large area end of the piston 58; 91/47, 5 in communication with the accumulator system.

ACTUATORS FOR PRESSURE LOADED VALVES BACKGROUND OF THE INVENTION bleed or pressure relief valves which are installed at the throat of a blast furnace. The present invention has also been found to be useful in the control of admission and exhaust valves for gas pressure equalizing chambers at blast furnace throats.

Prior art bleed valves of the type characterized by a mushroom-type obturator valve head which opens outwardly are maintained in the normally closed position by counterweights or spring assemblies; these mechanical devices compensating for the pressure of the blast furnace gases on the valve head. The closing forces imparted by the weights or springs must, of course, insure hermeticity when the valve is closed by means of exerting a closing force on the valve head which is suff ciently in excess of the counterpressure exerted by the furnace gases.

The prior art valves are opened, according to the particular system adopted, by a hand an cable winch, an electrohydraulic thrust device, a hydraulic cylinder connected either to a ram pump or to a set of hydraulic accumulators, by a pneumatic cylinder, by any other suitable operating device or by a combination of two or more of the aforementioned devices. In general, however, the prior art bleeder valve control systems were characterized by mechanical means, such as springs, for closing the valves and by hydraulic means such as hydraulic cylinder connected to a set of hydroelastic accumulators, for opening the valves. The valve opening mechanisms have typically included means whereby the opening of the valve is controlled automatically by the pressure of the blast furnace gases at the throat of the furnace. Such control means may, for example, comprise a system of adjustable pressostats which control the operation of the hydraulic cylinders to stop and start the admission of oil under pressure to the cylinder. The desired operational mode requires that the bleeder valves be opened at an intermediate pressure, the opening being achieved by overcoming the closing forces applied by the springs or other mechanical means. Opening should, of course, be at a pressure below that at which the pressostats have been preset and at which the. pressure of the furnace gases will overcome the mechanical closing forces.

The above briefly described prior art bleeder valve control systems have proved satisfactory up to effective pressures on the order of 1.5 kg./cm. The spring-hydraulic cylinder systems also offer an advantage in that the parts to be set in motion have very low inertia when compared with valves of the counterweight type and thus provide for rapid opening of the valves at reduced pressures. However, for the reasons to be briefly discussed below, even the most satisfactory of the prior art systems are characterized by serious deficiencies if the blast furnace on which they are installed is to be operated at an effective counterpressure of 3 or even 5 kg./cm.

Among the aforementioned deficiencies is the fact that the calibration of the closure springs in accordance with the operating pressure of the blast furnace can only be carried out locally, on the valves themselves, under dangerous conditions. In practice, it has been found that the spring calibration operation must be repeated whenever the working pressure of the furnace undergoes any appreciable change in order to insure that, in the case of any emergency operation such as the failure of the hydraulic equipment for the control, the gas pressure at the throat will not rise to a level which will result in damage to the plant before the valve is able to open. Also, it has been found practically impossible to design spring assemblies of acceptable dimensions which are capable of balancing out effective gas pressures on the order of 3 to 5 kg./cm.

SUMMARY OF THE INVENTION The present invention overcomes the foregoing and other deficiencies and disadvantages of the prior art by providing a bleed or pressure relief valve control mechanism which does not rely upon mechanical forces for maintaining the valve in the normally closed position. In accordance with the present invention, the function of the spring or other mechanical assemblies of the prior art is performed by the hydraulic cylinder which formerly served only to open the valve. The hydraulic cylinder is thus adapted to new conditions of operation in such a manner as to receive, on the rod or smaller area side of the piston, a pressure which is sufficiently large to subject the valve head to the stresses which were formerly applied thereto, under the same operating conditions, by the spring or other mechanical assemblies of the prior art.

As in the prior art, the opening of the valve will be effected by the application of fluid from a pressurized source to the head or large area side of the hydraulic cylinder piston. HOwever, in accordance with the present invention, a differential area piston is employed and the source from which pressure is applied to both sides of the piston may be the same accumulator system. Accordingly, the opening of the valve will be accomplished by means of a force unbalance which results from the application of pressurized fluid, usually from the same source, to the opposite and different active area ends of the piston. This force unbalance will be sufficient to overcome the sum of the closing forces resulting from the hydraulic force on the smaller area (rod) side of the piston, the weight of the valve obturator, the weight of the operating lever and other mechanisms and the forces due to any auxiliary springs.

The closing of a valve opened in the manner described above is achieved merely by discharging the oil contained in the cylinder on the head (larger area) side of the hydraulic cylinder piston whereby the valve will close as a result of the hydroelastic pressure maintained on the piston at the rod side.

In accordance with a second embodiment of the invention, a hydroelastic system similar to that described above is applied to valves employed for equalizing the pressure between blast furnace top bells, i.e. to the admission and exhaust valves of a double-bell-hopper arrangement. In this arrangement of furnace top-bells, the most suitable valves presently available are also characterized by a mushroom-type obturator which is closed and maintained in the normally closed position by a spring assembly, the obturator being opened toward the outside by means of a hydraulic cylinder connected to hydroelastic accumulators. The application of the integral hydroelastic system in accordance with the present invention enables the spring assemblies to be eliminated and higher operating pressures to be adopted.

BRIEF DESCRIPTION OF THE DRAWING The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to like elements in the various figures and in which:

FIG. 1 is a schematic diagram of a first embodiment of the present invention, the embodiment of FIG. 1 being shown in the environment of a bleed or pressure relief valve at the throat of a blast furnace; and

FIG. 2 is a schematic diagram of a second embodiment of the present invention, the valve control system of FIG. 2 being shown in the environment of a valve for equalizing the pressure between the top bells of a blast furnace.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to FIG. 1, the body ofa bleed pressure relief valve, as is typically found mounted on the gas takeoff at the throat of a blast furnace, is indicated generally at l. The valve body 1 comprises a valve seat 2 and a mushroom-type obturator or valve head 3. The obturator will typically have a deflector, not shown, that will cooperate with seat 2 to seal the gas takeoff port when the valve is in the closed position as shown.

The obturator 3 is connected, via a rod 4, to a control lever 5. Control lever 5 is pivotable about a fixed pivot point 6.

A differential area piston in hydraulic cylinder 7 is connected, via its piston rod, to control lever 5 at point 8. Hydraulic cylinder 7 is of the double-acting type and is connected on both its rod side and head side to the same system of hydroelastic accumulators 9.

As will be obvious to those skilled in the art, the pressure of the gas at the throat of the blast furnace will act on obturator 3 and tend to open the normally closed valve outwardly. In order to keep valve 1 closed and insure a hermetic closure, the load to which the obturator 3 is subjected by the pressure of the gas at the blast furnace throat is counterbalanced by a greater force exerted in the opposite direction via control lever 5 and rod 4. This closing pressure is a resultant of the application of pressure from the accumulator system 9 to the rod or smaller area end of the piston in cylinder 7.

In order to open the valve, the head end of cylinder 7 is placed into communication with accumulator system 9 via valve 11. This action applies the same pressure to both sides of the piston in cylinder 7. Owing to the difference between the effective areas of the two faces of the piston, oil under pressure on the rod side (small area) is forced toward the accumulator system 9 by the action of the oil at the same pressure acting on the free. face (large area) of the piston. Accordingly, the piston ascends and, via the lever 5 and rod 4, raises the obturator 3.

To reclose the opened valve, the pressure on the free face of the piston is relieved by placing the head end of cylinder 7 in communication with an outlet 10 via diversion valve 11. The piston will accordingly descend, under the action of the hydroelastic pressure maintained on the rod side thereof, and the obturator 3 is reseated.

It is to be noted that, in accordance with the present invention, instead of using a single set of hydroelastic accumulators, the ends of the hydraulic cylinder can be connected to two separate hydroelastic accumulator systems which exert equal or different pressures on the two faces of the piston in the cylinder.

It is also to be noted that the pressure in the accumulator system or systems can be regulated within a wide range, for example by means ofa control valve 12, and such pressure regulation may be done in complete safety in a hydraulic control room. The ability to remotely control the system provides a decided advantage in the event of an unexpected opening of the valve I; particularly when compared with prior art systems wherein the spring assembly had to be regulated locally.

If necessary or desired, as shown schematically at 13, a power closing" apparatus may also be employed in accordance with the present invention. If included, the power closing apparatus applies an additional force to the seal at the moment of closing of valve I, through the application of pressure to the rod side of the. piston, which is slightly in excess of that supplied by the accumulator system 9. The power closing apparatus will comprise a suitable valve system and source of hydraulic pressure.

Similarly, an auxiliary spring 14, calibrated to the normal effective pressure of the gas at the throat, i.e. 0.2%.3 kg./cm. can be employed in order to close the valve in the event ofany failure in the hydroelastic system. An operating device based on the use ofa cable winch, as shown schematically at 15, may be installed in order to effect opening operation in the event of any failure or breakdown in the hydroelastic system.

It is also to be noted that the system as described may be controlled remotely by various means such as the use of a solenoid 16 to control diversion valve 11. Other remote and/or automatic control arrangements will be obvious to those skilled in the art.

FIG. 2 shows a second embodiment of the present invention similar to that described above; the embodiment of FIG. 2 being shown in the environment of a valve used for equalizing the pressure between the top-bells at the throat of a blast furnace. In FIG. 2, the valve body 17 is mounted on the lock chamber between the top-bells of a blast furnace and, in the event of the operation of valve 17 as an admission valve, is connected to an equalization gas supply conduit. The valve body 17 is fitted with a seat 18 on which is mounted a mushroom-type obturator 19. The obturator 19 is attached to a piston rod which is in turn connected to the differential area piston in a double-acting hydraulic cylinder 7. The cylinder 7 is characterized by a pair of piston rods which extend from either end' thereof. The largest effective surface area of the piston in cylinder 7 is provided by the end from which the piston rod connected to obturator 19 extends.

It is to be noted that the larger diameter rod, i.e. the rod extending from the end of the piston in cylinder 7 having the smaller effective area, has an auxiliary spring 20 associated therewith. Spring 20 is calibrated to the effective pressure which the gas assumes at the blast furnace throat in the event of the furnace operating without any counterpressure at the throat.

In order to keep the valve 17 closed and insure hermeticity during closure, an appropriate force is exerted on the obturator 19 by the piston in cylinder 7 by means of subjecting the smaller effective area side of the piston permanently to the hydroelastic pressure furnished by accumulator system 9.

To open valve 17, the end of cylinder 7 facing the larger effective area of the piston is placed into communication with accumulator system 9 to thereby apply the same pressure to both sides of the piston. Owing to the difference between the effective areas on the two faces of the piston, application of the same pressure to both sides thereof will result in the piston ascending, as shown in FIG. 2, and the valve thereby being opened.

To reclose the opened valve, the lower end of cylinder 7 is placed in communication with an outlet 10 via a diversion valve '11. The piston will accordingly descend, under the effect of the hydroelastic pressure maintained on the other side of the piston, and the obturator 19 will be reseated against valve seat 18.

The operation of valve 17, at the rhythm selected for the valves of the pressure equalization system between the furnace top-bells, is controlled by an automatic servocontrol system, indicated schematically at 16, in accordance with the sequence of the blast furnace charging program.

The above-described valve control apparatus in accordance with the present invention is applicable both to the admission valve and to the exhaust valve of the pressure equalizing system at the blast furnace throat. Thus, it may be seen that the present invention has been described by way of illustration and not limitation and various modifications and substitutions may be made thereto without departing from the spirit and scope ofthe invention.

What I claim is:

1. An actuator for a normally closed valve, said valve including a valve head and a seat and said valve head normally being subjected to forces in the opening direction, said actuator comprising:

a cylinder;

a differential area piston disposed in said cylinder, said piston being in sealing relationship to the walls of said cylinder and having a piston rod which extends out of a first end of the cylinder from the smaller area end of said piston;

means mechanically connecting said piston rod to said valve head, said connecting means including a lever arm mounted for pivoting about a first end and means connecting said lever arm to said piston rod adjacent the other end of said lever arm, said valve head being connected to said lever arm intermediate said first end and said piston rod connection;

a source of pressurized fluid, the fluid source including hydraulic accumulator means;

means permanently coupling the output of said accumulator means to said first end of said cylinder whereby said piston normally urges said valve to the closed position; and

normally closed valve means connected between accumulator means output and the other end of said cylinder, said valve means having a first operative state whereby said second end of said cylinder may be placed into communication with said accumulator means and the pressurized fluid will act on the larger area end of said piston and said piston will be caused to move in a first direction thereby opening said valve, said valve means having a second operative state whereby fluid in said cylinder at said larger area side of said piston may be relieved and said valve will be urged in the closed direction through the action of said fluid on said smaller area end of said piston.

2. The apparatus of claim 1 further comprising:

means connected to said lever arm for mechanically biasing said valve head in the closed direction. 

1. An actuator for a normally closed valve, said valve including a valve head and a seat and said valve head normally being subjected to forces in the opening direction, said actuator comprising: a cylinder; a differential area piston disposed in said cylinder, said piston being in sealing relationship to the walls of said cylinder and having a piston rod which extends out of a first end of the cylinder from the smaller area end of said piston; means mechanically connecting said piston rod to said valve head, said connecting means including a lever arm mounted for pivoting about a first end and means connecting said lever arm to said piston rod adjacent the other end of said lever arm, said valve head being connected to said lever arm intermediate said first end and said piston rod connection; a source of pressurized fluid, the fluid source including hydraulic accumulator means; means permanently coupling the output of said accumulator means to said first end of said cylinder whereby said piston normally urges said valve to the closed position; and normally closed valve means connected between accumulator means output and the other end of said cylinder, said valve means having a first operative state whereby said second end of said cylinder may be placed into communication with said accumulator means and the pressurized fluid will act on the larger area end of said piston and said piston will be caused to move in a first direction thereby opening said valve, said valve means having a second operative state whereby fluid in said cylinder at said larger area side of said piston may be relieved and said valve will be urged in the closed direction through the action of said fluid on said smaller area end of said piston.
 2. The apparatus of claim 1 further comprising: means connected to said lever arm for mechanically biasing said valve head in the closed direction. 